This invention relates to a disposable medical electrode which provides extended use in a high humidity environment. More particularly, this invention relates to an ECG, or the like, electrode which is suitable for use on neonatal patients who are placed in a high humidity incubator environment. The electrode of this invention will not prematurely disengage from the neonate""s skin due to hydrogel member water absorption from the high humidity environment.
Medical electrodes are widely used for the measurement and monitoring of ECT, EEG, EMG, ENG and impedance pneumography in hospitals. These electrode assemblies are used for both adult and neonatal patients, and are fastened directly to the skin of the patient for sensing of the respective electrical signals emanating from the patient""s body. The electrodes most widely used at the present time, include a silver-silver chloride sensor having a signal transmitting line connected thereto, and mounted in an electrically conductive, self adhesive hydrogel member. The hydrogel provides a conductive connection between the patient""s skin and the sensor so that electrical signals emanating from the patient""s body will be sensed by the sensor. The signal transmitting line is connected to a monitor, such as an oscilloscope, or the like, which provides a readout of the the sensed electrical signals from the patient. The electrode may necessarily be used to monitor a patient for a relatively long period of time, therefore, it is critical that the intimate contact between the patient""s skin and the electrode, which is provided by the conductive, adhesive hydrogel, be stable over the monitoring period. In most environments, stability of the patient-electrode contact is not a problem, and extended monitoring utility is obtainable.
One environment which has caused problems with the aforesaid adhesion stability is a newly developed high humidity incubator environment that is used for care of neonates. A high humidity environment is becoming a preferred method for combating trans-epidermal water loss (TEWL) in low birth weight (about six hundred to about fifteen hundred grams) neonates. Due to the fact that these neonates have skin that is very underdeveloped, two problems arise. TEWL is the first. Water escapes very easily through the skin, resulting in dehydration. xe2x80x9cSwampingxe2x80x9d is used to combat excessive TEWL by reducing the moisture gradient between the patient and the ambient environment. By elevating the ambient humidity, water is much less likely to migrate through the skin. Secondly, the underdeveloped skin is prone to damage, leading to possible infection and death. Aggressive adhesives cannot be used on vital signs-monitoring devices due to the delicate condition of the skin.
The relative humidity in such incubators is in the range of about 50% to about 90%. The conductive, adhesive hydrogel member of the electrode, as noted above, is hydrophilic, and thus is prone to absorption of water from the highly humid atmosphere in the newly developed incubators. The result of placing the electrode hydrogel member in the high humidity environment of the aforesaid newly developed incubator is absorption of water by the hydrogel member, and subsequent erosion of the adhesiveness of the hydrogel. The electrode will thus simply fall off of the neonatal patient if left in the high humidity incubator environment for a time period which can be as short as one to two hours. It would thus be highly desirable to provide an electrode which displays extended adhesion to the skin of a neonate in the high humidity environment of the currently used incubators.
This invention relates to a medical electrode of the character described which has enhanced skin adhesion in a high humidity environment. The electrode of this invention includes the conventional sensor and electrical lead. A self adhesive conductive hydrogel member surrounds the sensor and serves to provide enhanced signals to the sensor. The hydrogel member is surrounded by an adjunct adhesive component which will not absorb significant amounts of water from the high humidity environment in the incubators. The adjunct adhesive component is preferably a relatively hydrophobic material and it is adhered intimately to the conductive hydrogel while allowing the conductive hydrogel to maintain its intimate contact with the neonate""s skin. The adjunct adhesive component protects the conductive hydrogel member against excessive water absorption, and also enhances and stabilizes the adhesive bond between the electrode and the neonate""s skin. One configuration of the adjunct adhesive component which has proven to be exemplary is an annular, or donut, shape.